Solutions – Nitrogen/Argon Gas Treatment

Brief description of treatment

Nitrogen (N2) and argon (Ar) gas used in controlled atmospheres are effective in causing insect death within 2-6 weeks, as shown by measuring insect respiration before and after treatment. In order for Nitrogen/Argon treatment to work, the oxygen levels are reduced to 0.1-0.3%. The oxygen deprivation causes a disruption in the glucose production within insect bodies, resulting in weight loss and eventual insect death. Rates of death vary with temperature, relative humidity, exposure time, and species type. Increasing the temperature helps reduce the exposure time for both gases because insect respiration is increased with higher temperature, causing rapid water loss. (Valentín 1993). Argon is 25-50% faster than nitrogen at killing insects. Additionally, argon kills some fungal tissue while nitrogen permits the same fungi to survive anoxia (Koestler, Tavzes, Pohleven 2004). Modified atmospheres using nitrogen and argon are usually continuous-flow systems with soft or hard walled, vapor impermeable chambers. The continuous flow of gas initially purges the chamber of oxygen, and then maintains low oxygen levels to compensate for leaks.

What collections materials can be treated this way?

Almost all collections can be treated with nitrogen or argon.  Exceptions include:

  • One study showed that minerals such as litharge (PbO), cinnabar (HgS), and sienna (mostly Fe2O3) do experience color change in the absence of oxygen (Arney, Jacobs, and Newman 1979), so care must be taken if this is a concern with artifacts or pigments. Prussian blue and ultramarine initially change, but the color comes back. Changes are not noted when pigments are in mixtures, e.g., in paint films. Textiles may be the most likely to change (temporarily).
  • Wet artifacts have the potential to reduce the effectiveness of treatment due to insect adaptation to use anaerobic respiration, although this is generally unlikely for the types of pests typically encountered for museum and library pests (Selwitz 1998).
General procedures
An anoxic atmosphere requires an enclosure, gas, and gas monitoring devices. Uses low-oxygen gas (less then 1000ppm of O2). Enclosures must be constructed of vapor impermeable materials such as steel or aluminized polyethylene and polypropylene films. There are several types of enclosures: hard-wall, soft-wall, and mobile chambers (see below.)
Procedures vary by chamber type, but all include:
  1. Load the chamber so artifacts cannot crush each other, accidentally shift, or be crushed by the walls of a soft chamber.
  2. Seal the chamber (heat-seal for soft wall chambers, zipping shut for retrofitted fumigation soft wall chambers, and closing the door on a hard wall chamber ensuring the gasketry is in good alignment and condition).
  3. Purge ambient air and oxygen from the chamber. Sometimes this is a two-step procedure; first, introduction of nitrogen to push out the oxygen, followed by the secondary anoxia gas like argon or nitrogen. However, in larger chambers, this additional step has not proven to be necessary since many larger chambers have constant positive pressure to maintain low oxygen levels.
  4. Monitor and maintain constant gas flow for the duration of the treatment. Treatment duration depends on gas type and species of insect if known.
  5. Evacuate the anoxic gas from the chamber and return ambient air, while observing proper safety protocols to maintain safe levels for humans.
  6. Examine artifacts followed by removal of dead insect debris by low suction HEPA vacuuming or using tweezers.
Pros of this treatment
  • No chemical residue on artifacts.
  • Appropriate for a wide variety of collection materials.
  • Argon gas has the additional benefit of preventing bio-deterioration by microorganisms like fungi and bacteria (Valentín 1990).
  • More time-efficient than CO2 gas.
  • The EPA does not currently list argon and nitrogen as a registered pesticide, so users must research and follow state guidelines for the determinations and requirements for defining what gases are pesticides and if applicator licenses are necessary. This is based on the applicator’s residency and the entity that needs to perform the treatment. For the most up to date information, refer to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) on http://www.epa.gov/pesticides/regulating/index.htm
Cons of this treatment
  • Generally, treatment with argon or nitrogen gas is more costly than treatment with CO2 gas, depending on regional rates for gas acquisition
  • Nitrogen can in some cases contribute to growth of microorganisms with nitrogenase enzymes that help fix nitrogen as a fuel source. More research is needed in this area to clarify this potential issue.
Materials, supplies, product manufacturers
Hard wall chambers:
  • Typically steel shell chambers or rooms hard-wired into building electrical and HVAC systems, and become a permanent fixture of the internal building.
  • Chambers usually use nitrogen or CO2.
  • Include a sealable door in which shelves or carts of infested materials can be inserted. Doors should be secured.
  • Suppliers:
Soft wall chambers:
  • Constructed of a vapor impermeable film (also referred to as a barrier film) that is heat set together at the seams.
  • Very large soft-walled chambers may have an internal frame support of wood or PVC piping to prevent collapse on the artifact(s).
  • Can be made to any specific size or shape in-situ, which is helpful for odd-shaped or large objects.
  • Reusable soft wall chambers are usually chambers previously manufactured for chemical fumigation techniques that are no longer used or permitted by law (such as methyl bromide) and retrofitted for other gases like nitrogen, argon or CO2. Use an external gas supply.
  • Suppliers:
Mobile chambers:
At least one institution has investigated the possibility of developing a mobile self-contained custom-sized trailer system. The system as proposed would have had the following capabilities:
  • 8’ x 8’ x 14’ Trailer chamber with trailer door that can be secured and sealed airtight.
  • Both a generator and capacity for a building power source connection
  • Electrical, temperature and relative humidity monitoring
  • Loading ramp
  • Auto-injection and recycle of Argon gas
  • Maintain 0.1 – 0.5% O2 level
  • External monitoring panels
Additional Supplies
  • Barrier films for chambers (available from several vendors, search internet for the following products):
    • Aclar, Marvelseal, and Escal are available from numerous preservation and commercial vendors.
  • Heat sealers for vapor barrier film (available from several vendors, search internet for the following products):
    • constant heat hand sealers
      • Futura Cello Model Sealer, 6″ long, top and bottom heated hand sealer with 3 temperature settings.
    • Heat spatulas
      • 21st Century Tacking Iron
      • Coverite Trim Sealing Iron
Selected bibliography
Arney, J. S., A. J. Jacobs, and R. Newman. 1979. Influence of oxygen on the fading of organic colourants. Journal of the American Institute for Conservation 18:108-17. http://cool.conservation-us.org/jaic/articles/jaic18-02-004_indx.html

Burke, J. 1996. Anoxic Microenvironments: a simple guide, Society for the Preservation of Natural History Collections (SPNHC) leaflet 1(1): 1-4. Available from www.spnhc.org.

Daniel, V., Hanlon, G., and S. Maekawa, 1993. Eradication of Insect Pests in Museums Using Nitrogen. WAAC Newsletter 15(3):15-19. Western Association for Art Conservation.

Gilberg, Mark, 1991,The Effects of Low Oxygen Atmospheres on Museum Pests, Studies in Conservation (36):93-98.

Hanlon, G. Daniel, V. & Ravenel, N. “Dynamic System for Nitrogen Anoxia of Large Museum Objects: A Pest Eradication Case Study”, Proceedings of the Second International Conference on Biodeterioration of Cultural Property, Oct 5-8, 1992, Yokohama, Japan.

Koestler, R.J., 1992. Practical application of nitrogen and argon fumigation procedures for insect control in museum objects. Toishi, K., Arai, H., Kenjo, T., Yamano, K. (eds.) 2nd International Conference on Biodeterioration of Cultural Property, Yokohama, Japan, 5-8 Oct 1992, preprints pp 94-96.

Koestler, R.J., 1993. Insect eradication using controlled atmospheres, and FTIR measurement for insect activity. ICOM 10th Triennial Meeting, Washington, D.C. Vol. II, 882-886.Koestler, R.J., 1996. Anoxic treatment for insect control in panel paintings and frames with argon gas. American Institute of Conservation Paintings Specialty Group, Postprints. AIC, 1717 K Street, NW, Suite 301, Washington DC 20006, 61-72.

Koestler, R.J., Sardjono, S., and Koestler, D.L., 2000. Detection of insect infestation in museum objects by carbon dioxide measurement using FTIR. International Biodeterioration and Biodegradation, 46, 285-292.

Sardjono, S., Koestler, D.L., and Koestler, R.J., 2000. Detection of hidden insects in museum objects by carbon dioxide measurement using FTIR. Student papers: 26th conference of the Association of North American Graduate Programs in Conservation. Smithsonian Center for Materials Research and Education. Washington, D.C., 72-76.

Koestler, R.J., C. Tavzes, and F. Pohleven, 2004, A New Approach on the Conservation of Wooden Heritage, International Research Group on Wood Preservation, Paper prepared for the 35th Annual Meeting, Ljubljana, Slovenia, 6-10 June, 2004, available through IRG Secretariat, Stockholm, Sweden.

Koestler, R.J., Parreira, E, Santoro, E.D., and Noble, P., 1993. Visual effects of selected biocides on easel painting materials. Studies in Conservation, 38, 265-273.

Suzuki, J., and Koestler, R.J., 2003. Visual assessment of biocide effects on Japanese paint materials. In: Koestler, R.J., Koestler, V.R., Charola, A.E., and Nieto-Fernandez, F.E., (Eds.), Art, Biology, and Conservation: Biodeterioration of Works of Art. The Metropolitan Museum of Art, New York, Yale University Press, New Haven, 410-425.

Met Objectives. 2002. “Biodeterioration in Museum Collections” Sherman Fairchild Center for Objects Conservation. Metropolitan Museum of Art. 3(2).

Selwitz, C. and S. Maekawa 1998. Inert Gases in the Control of Museum Insect Pests. Los Angeles: The Getty Conservation Institute. http://www.getty.edu/conservation/publications/pdf_publications/inertgases.pdf

Valentín, N. 1990. Insect eradication in museums and archives by oxygen replacement, a pilot project. ICOM Committee for Conservation 9th Triennial Meeting, Dresden, German Democratic Republic, 26-31 August 1990, Preprints, vol. 2, ed. K. Grimstad. Los Angeles: ICOM Committee for Conservation. 821-23.

Valentín, N. 1993. Comparative analysis of insect control by nitrogen, argon, and carbon dioxide in museum, archive, and herbarium collections. International Biodeterioration and Biodegradation 32:263-78.

Material Safety Data Sheets (MSDS)

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